Support tube



FIG. 1 is a top isometric view of a support tube incorporating my new design;

FIG. 2 is a front elevation view thereof

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a right side elevation, view thereof, the left side elevation view being a mirror image thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a bottom isometric view thereof.

The broken lines in the drawings represent portions of the support tube that form no part of the claimed design. 

CLAIM The ornamental design for a support tube, as shown and described. 